Volt drop question

[La Poste]

Greetings.

Let's say you have a 2.5mm cable that you want to extend by quite a long run.
After looking at your load and volt drop calculations you arrive at a cable size for the extension of 6mm.

Would it be bad practice to add a 6mm extension to the end of a 2.5mm cable?

The circuit protection would be calculated to protect the 2.5mm cable IE a 20 Amp circuit breaker, the only reason to use the 6mm cable is simply for volt drop issues.

It is not possible to lay a new cable from the board, this is the only option.

I can't see anything in the regulations to say this is wrong but I was wondering what people thought about this.

Thanks.

 

[yellowvanman]

can't see a problem with this myself, just put a note in your cert!

 

[PC Electrics]

agree with YV.

 

[Knobhead]

So long as the protection is correct for the smallest conductor. Where’s the problem?

 

[telectrix]

thinking laterally, we regularly fit 25mm tails to 16mm DNO supply cables.

 

[rich.250]

Was told once you can't do this as it will draw to much power and trip CB!! LOL

Utter non sense, the things you believe when your young lol

Agree with the above posts
Perfectly ok.

 

[La Poste]

Thanks.

Now all I have to work out is how to do the volt drop calcs properly IE calculating the volt drop at different parts of the circuit and also apply diversity to arrive at my load current.

This is a good thread:
http://www.electriciansforums.net/e...ations/55221-voltage-drop-outside-lights.html

Is the 3% volt drop for lighting circuits set in stone?

Is 3% the absolute limit or in the real world do you allow a little more?

 

[telectrix]

in the real world we have a supply of 240v, which allows 4% drop to reach the magical hypothetical 230v on which calculations are based. tin hat on.

 

[yellowvanman]

Thanks.

Now all I have to work out is how to do the volt drop calcs properly IE calculating the volt drop at different parts of the circuit and also apply diversity to arrive at my load current.

This is a good thread:
http://www.electriciansforums.net/e...ations/55221-voltage-drop-outside-lights.html

Is the 3% volt drop for lighting circuits set in stone?

Is 3% the absolute limit or in the real world do you allow a little more?

The 3% for lighting and 5% for other circuits is a rule of thumb if you don't know the voltage limits of what you are connecting. If you do know the operating voltage of a piece of equipment then you can size the cable accordingly.

eg. if the working voltage of a machine is 180V - 250V then you can 'lose' up to 50V, assuming your input voltage is 230V

 

[sedgy34]

note it on cert